1. Field of the Invention
The present invention relates to a surface mounting type coil, and more particularly relates to the surface mounting type coil which is used in a noise elimination filter of an interface in an LAN (Local Area Network), or a communication between computers or terminals and the like.
2. Description of the Related Art
FIGS. 11 and 12 show examples of this type of surface mounting type coil.
FIG. 11 is a perspective view of a conventional surface mounting type coil comprising a toroidal core. Windings 63 comprise a primary winding and a secondary winding, and are wound around a toroidal core 61. A plurality of external terminals 65 function as terminals for binding ends of the windings and terminals for external connection, and are provided on a base 62. The binding leads 66 of the windings 63 are bound and soldered to the external terminals 65.
Recently, there is a strong demand to reduce noise emission and interference. This type of surface mounting type coil has a problem of magnetic flux leakage from the binding leads 66 of the windings 63, with consequent deterioration in the characteristics.
Generally, surface mounting type coils are attached and soldered to a printed circuit board by using an automatic attaching apparatus and a reflow soldering apparatus respectively. As a consequence, when there is considerable variation in the extent and thickness of the solder of the binding leads 66, which are bound to the external terminals 65, the external terminals 65 become nonflat. This causes warping, pitch deviation, and the like in subsequent processing, and some of the external terminals 65 make gaps to a circuit board when the coil is mounted thereon. Further, the terminals 65 deviate from the interconnection patterns on the circuit substrate, causing malfunctions such as connection failure and short-circuiting.
FIG. 12 is an exploded perspective view of another conventional surface mounting type coil comprising a toroidal core. The dotted lines in FIG. 12 represent the configurations of the terminals inside a resin base. Windings 73 comprise a primary winding and a secondary winding, and are wound around a toroidal core 71 and secured to a base 72. As shown by the dotted lines, binding terminals 75a are connected inside the base 72 to external terminals 75b. The binding leads 76 of the windings 73 are connected to the binding terminals 75a by soldering or the like.
This type of surface mounting type coil 73 has a problem of magnetic flux leakage from the binding leads 76 of the windings 73, with consequent deterioration in the characteristics. Further, since the binding terminals 75a and the external terminals 75b are connected together inside the base 72, the increased dc resistance causes loss. Moreover, since neither of the above examples can be adsorbed by an automatic attaching apparatus, they require a chuck constitution to enable their sides to be held by chucking or the like, and must be handled carefully.